1. Field of the Invention
The present invention relates to a transparency for reproducing area delineations of colored areas of a pattern on a display in an optical viewer. The transparency is made of a photopolymerizable material with mutually exclusive areas, each individual area representing a variable color wherein each area repesenting a particular variable color has encoded therein preselected angularly oriented spatial frequency carriers created holographically by the interference of a split laser beam.
2. Description of the Prior Art
In many industries and especially in the textile industry a designer for styling purposes has a need for viewing different color combinations of a pattern in which each color may be individually manipulated at will through the entire range of color. Systems have been proposed which enable selected color combinations of a pattern to be viewed on a visual display. An example of such a system is an optical viewer which utilizes a light source and a photographic plate. The photographic plate encoded encodes with a spatial frequency carrier for each area for the pattern, with the encoded areas diffracting light from the light source to reproduce the pattern on a display. The light is colorable and enables the pattern to be colored in a variety of color combinations. It is further known to use a camera to photograph the displayed pattern to make a proof.
In the past the encoded frequency carrier used in the above-described system has been prepared using silver halide based systems. The technique involves focusing a Ronchi ruling on an emulsion containing the silver halide to expose the silver halide followed by developing the exposed silver halide. This type of diffraction grating cannot diffract more than about 7% of the light passed therethrough into the first order of diffraction. Because of this these diffraction gratings are often bleached to change the silver halide into a transparent salt with a different index of refraction than the emulsion creating a phase diffraction grating medium having improved diffraction efficiency. The bleaching process often produces imperfections in the gratings which results in "noise" when light is passed through the grating. In either case the resulting diffraction grating consists of lines of emulsion which are rectangular in cross-section and usually about 10-15 microns in thickness supported on a transparent support such as glass or organic resin film. The rectangular cross-section of the grating lines in either type grating in effect gives them a multiple frequency and produces many orders of diffraction. The use of a Ronchi grating places a practical limit to the spacing of the lines to a maximum of about 200 lines per millimeter. A thin phase grating can theoretically diffract up to about 33% of the light passed therethrough into the first order of diffraction, but in practice the amount for a bleached grating is usually in the range of 15 to 20%. It is desirable to increase the amount of light passed into the first order of diffraction and additionally to eliminate the higher orders since they must be blanked out.